A variety of herbicides have been used to kill unwanted plants (weeds) in crop fields or orchards. Typically, these herbicides are sprayed onto the soil (pre-emergence) or onto the plants (post-emergence).
Herbicides are expensive, and their use may result in unintended consequences such as groundwater contamination, crop damage, environmental damage, spray drift, and human and mammalian health concerns.
There are many classes of herbicides that may be grouped based on their mode of action. One class of herbicides of particular interest are the bipyridylium salts. These compounds inhibit photosystem I (PSI) and are exemplified by paraquat and diquat. Paraquat is marketed under many names in the US including Gramoxone® and Gramoxone Extra®, while diquat is marketed under several names including Reglone® and Reglox®. Bipyridylium salts act by diverting electrons from PSI of photosynthesis and are subsequently reduced by molecular oxygen. This results in the generation of superoxides and related free-radical species. The cellular damage resulting from free-radical oxidation kills the plant.
There are many compounds that may be classified as inducers of plant systemically acquired resistance (SAR). Although these compounds fall into many structural classes, all of these compounds or mixtures of compounds are able to increase the resistance of plants to pathogen attack. Many of these SAR inducers cause changes in the salicylate-dependent pathway of resistance (ie. Harpin), others may mimic salicylate (ie BTH), or others may induce resistance through ethylene and jasmonate dependent pathways (ie ethephon).
It is an object of the present invention to safen crop plants from unintended herbicidal consequences of paraquat and diquat application. It is also an object of this invention to lessen the effects of spray drift on non-target species when these herbicides are used.